Fenders (also known as rub rails, rub guards, and bumpers) are commonly used to facilitate sliding and prevent damage to a boat or other vessel when rubbing or bumping against structures, such as pilings and docks. Fenders are typically attached along the hull of a boat, but may also be attached to docks, pilings, seawalls, bridge footings, and other structures against which a vessel may rub or bump. Fenders are also used to protect other objects from damage due to rubbing and bumping—especially warehouse loading docks and land vehicles, such as truck trailers.
A fender system used with many military and commercial ships includes a length of half round steel pipe (hereinafter “split pipe”) extending along the hull and welded to the outside of hull to form a raised rib. A relatively smooth outer surface of the fender is desirable for sliding maneuvers such as docking, when the vessel is sliding along another object, such as a piling or dock. In these sliding maneuvers, any dents or discontinuities in the outer surface of the split pipe fender can inhibit a smooth sliding action by converting the desired longitudinal motion into an undesirable athwart ship motion, thereby causing the vessel to move away from the piling surface along which sliding is intended to occur. Dents in the split pipe can also cause impact loads to be concentrated at a small location on the hull, rather than dispersing loads across a relatively large area. The strength of the split pipe determines the energy absorption capability of the fender system in impact situations. When impacts occur that exceed its strength, the steel permanently deforms, leaving a dented outer surface. Such dents must be repaired to maintain a smooth sliding surface. Furthermore, the outer surface of the split pipe is typically painted and requires regular repainting and maintenance to prevent corrosion and other causes of failure, even in the absence of severe impacts.
Pleasure boats commonly have a light-duty fender system that includes strips of elastomer material seated in retainer channels or brackets along the sides of the hull. One such light-duty fender system is described in U.S. Pat. No. 2,959,146 of Erkert. Such fender systems are able to maintain a smooth sliding surface without discontinuities because the elastomer material is resilient. However, elastomer materials have a higher coefficient of friction than painted steel. Consequently, elastomer fenders do not slide as easily as split pipe fenders. Friction effects become even more pronounced when the elastomer is compressed, as during high impact conditions. The elastomer material also has limited abrasion resistance. In certain situations, the elastomer can be pulled out of its retainer, thereby making the fender system ineffective. Such fender systems also have a lower impact absorption capability than split pipe fender systems, and can allow impact forces to be transferred to the hull and cause damage.
U.S. Pat. No. 4,084,533 of Boyer describes a reversible rubrail for boats and ships that is formed of a unitary strip of extruded rubber or flexible plastic material. The rubrail includes a rear wall for connection to a boat and a pair of front walls extending from top and bottom edges of the rear wall in an arcuate shape to overlap along free ends of the front walls. The front walls are flexible and can be folded back to allow screws, bolts, or staples to be inserted through the rear wall for installation of the rubrail. Because the material of the front walls must be soft enough to be manually folded back for installation, the rubrail of Boyer would also suffer from the high coefficient of friction and low abrasion resistance of conventional elastomer strip fender systems.
The present inventor has recognized a need for a fender that can absorb a substantial amount of energy, that is highly resistant to permanent deformation and abrasion, has a low coefficient of friction, is easily installed, and requires little or no maintenance.